1. Field of the Invention
The present invention relates to a swing arm pivot structure for a motorcycle.
2. Description of Background Art
A conventional swing arm pivot structure for a motorcycle known in the art includes a pivot shaft threadedly engaged with a body frame and a nut member threadedly engaged with the pivot shaft, wherein the nut member is engageable with the body frame so as to be unmovable in one axial direction (see Japanese Patent Laid-Open No. 2006-96272, for example).
Another conventional swing arm pivot structure for a motorcycle known in the art includes a pivot shaft supported at its central portion to a through hole of an engine and a pair of collars mounted on the pivot shaft on the opposite sides of the central portion for rotatably supporting a swing arm, wherein a pair of large-diameter holes are formed at the opposite ends of the through hole of the engine, each large-diameter hole having a diameter larger than that of the through hole, and each collar is provided at its one end with an engaging portion for engaging each large-diameter hole (see Japanese Patent Laid-Open No. 2006-264460, for example).
In the swing arm pivot structure described in Japanese Patent Laid-Open No. 2006-96272, a tapered bearing is used to prevent rubbing between the swing arm and the body frame in swinging the swing arm, so that there is a possibility of an increase in manufacturing cost.
In the swing arm pivot structure described in Japanese Patent Laid-Open No. 2006-264460, the plural collars are required to prevent rubbing between the swing arm and the body frame, and the through hole for insertion of the pivot shaft must be formed in the engine. Accordingly, the structure is complicated to cause the possibility of an increase in manufacturing cost.